


1 New Message

by MorgannaGrim



Category: Trainspotting (Movies), Trainspotting Series - Irvine Welsh
Genre: Catfishing, Flat mates, Friends to Lovers, Grindr, M/M, Pining, Post T2, T2
Language: English
Status: In-Progress
Published: 2020-07-18
Updated: 2021-03-03
Packaged: 2021-03-05 04:41:40
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 4,641
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25358638
Author URL: https://archiveofourown.org/users/MorgannaGrim/pseuds/MorgannaGrim
Summary: Under any normal circumstance he wouldn't give two shits about what Mark Renton's few and far between friends had to say but three texts in seven minutes was enough to pique even Simon's interest.
Relationships: Mark "Rent Boy" Renton & Simon "Sick Boy" Williamson, Mark "Rent Boy" Renton/Simon "Sick Boy" Williamson
Comments: 7
Kudos: 40





	1. 1

Simon had desperately tried to mind his own business when Mark's phone chimed obnoxiously from the kitchen counter top of their now fully co-habituated flat. He cast a curious glance in the general direction of the iPhone that Mark had carelessly abandoned ten minutes prior in favour of a shower. “Clean body, clean mind, Si,” He'd called over his shoulder on his way into the bathroom. “Ye should try it.”

Under any normal circumstance he wouldn't give two shits about what Mark Renton's few and far between friends had to say but three texts in seven minutes was enough to pique even Simon's interest. He filled the kettle, fished himself and Mark a mug from the cupboard and came to rest casually against the counter beside Mark's phone where he definitely was _not_ trying to talk himself out of checking his best friend's notifications. _'Since when dae I give a fuck what the cunt gets up tae?'_ he had reasoned with himself only to counter his own point seconds later with a _'could be his Da. Could be an emergency like; a better check. Just incase.'_ and with that Simon found himself pressing a thumb to the side of Mark's phone, eyes scanning the screen as it illuminated.

**4 new notifications:**

  * **Screen Time: Weekly Screen Report Available**

  * **Grindr: 1 New Message**

  * **Grindr: 1 New Message**

  * **Grindr: 1 New Message**




_'Fuckin' Grindr? What the fuck is he daein on Grindr?...is he-'_ Simon was ripped from his thoughts by the sound of the bathroom door creaking open ever so slightly and Mark calling out for help.

“Si? Could ye git us a towel? A forgot tae bring one in wae us.”

“Uh... wha-? I mean.. aye. Aye, I'll get yae one now.” he called back and okay, maybe he sounded weird and maybe Simon was having some what of a hard time convincing his head catch up with the fucking rest of him but... _Grindr..._ Mark fucking Renton was on _Grindr._

Their evening was quiet; a Connery marathon and little to no chit-chat. Simon was thankful to say the least. It wasn't that he cared- _'It's no like a mind if he's a buftie.'_ he thought, unable to focus his full attention on the film in front of him.

' _A just wish he'd ae spoken tae us aboot it.'_ Simon was hurt, that was it. That's all it was; he was hurt that his best friend hadn't felt comfortable enough to confide in him. He was hurt that-

Mark's phone had chimed again in his pocket and Simon couldn't help but stare as the secretive wee cunt across from him fished his phone out of his pocket to read the message. Simon watched as Mark's mouth pulled itself into a modest smirk and he quickly typed out his reply before planting his phone firmly back in his pocket.

“Somethin' funny?” Simon found himself asking, an undeniable bite to his tone.

Mark only responded with a shrug, his eyes barely leaving the TV. _'Oh, aye. Cunt's got time tae look at his phone and reply tae his boyfriends but won't even look in my fuckin' direction when am speakin' tae him.'_

Simon wasn't jealous. He really wasn't; he was just... concerned? Mark was his mate, his _best_ mate. Always had been and it was highly likely that he always would be. Si couldn't shake the cunt and truth be told he wasn't sure he wanted to. He had grown used to having Mark around again, though the Mark he knew now was a stark contrast to the Mark he had known when they were still wains. This Mark was bigger, stronger; both physically and emotionally. He was domesticated and responsible. This Mark was holding down a job, paying his rent on time, keeping their flat clean, cooking dinner, ironing his fucking boxers for christ's sake. This Mark was _his_.

Simon shoved himself up from his slumped position across their couch and mumbled nothing more than “Am goin' tae bed.” as he retreated to the dark, quiet confines of his bedroom; door slamming behind him before Mark had a chance to respond. Simon needed time alone, time to think and process all of the information he had acquired in the last four hours. _'Fuckin' Grindr. What if he's meetin' up wae psychos? Doss cunt's gonnae get himsel killed.'_ Simon didn't know much of anything about dating apps; Tinder, Grindr, Bumble, Hinge... ' _all ae load ae old pish!'_ but he knew enough to know they could be dangerous and honestly? He couldn't fucking stand the thought of anything happening to Mark. He couldn't lose him again. He _refused_ to lose him again; Not this time.

That is how Simon Williamson found himself staring down at his own phone, deep in thought as his thumb hovered apprehensively over the download icon for Grindr. He was just being cautious. Just looking out for his best friend and making sure he wasn't being lured in by the Begbie's of the world; ' _Meetin' up wae fellas expectin' ae quick shag an' windin' up wae yer heed kicked in instead.'_

With a deep breath, he took the plunge and watched as the app planted itself firmly on his home screen, wee yellow face fucking smirking up at him. _'Cunt.'_

The sign up process hadn't been as long and arduous as Simon had anticipated; a few minor details entered, location and notifications turned off and a quick photo of his chest uploaded to his profile, he was set. Mark's profile was easy enough to locate; another shirtless torso but Simon knew what to look for, immediately recognising his friend's undeniably attractive torso and the scar from Mark's surgery. Mark didn't have a bad body, Si would give him that. Broad shoulders, toned biceps and a light dusting of chest hair all combined with strong, trim abs; aye... he could see the appeal ( _not that he was a wee buftie mind_ ).

**Mark (48) Online Now.**

**Bartender, traveller, fitness enthusiast based in Edinburgh.**

**Looking for mates, dates & anything in between. **

**Weight:** 175lb

 **Height:** 5'10

 **Body Type:** Toned

 **Gender:** Cis Man

 **Prnonouns:** He/Him/His

 **Position:** Vers Top

 **Tribes:** Rugged, Daddy, Discreet

Simon found himself biting his lower lip in attempt not to laugh as he read through Mark's profile, thumb flicking back and forth between the other man's photo and his bio. “Never would ae pegged yae as a Daddy type, Rent Boy.” Simon mumbled, tapping to exit out of Mark's profile with every intention of calling it a night but oh... _oh..._ “Wit the fuck is ae tap?... how do I undo a tap?.. wit have ae done?” Simon's phone buzzed in his hand, alerting him to a new message; his _first_ message in fact.

**Mark** >> Thanks for the tap. Great pic.

Fuck. What the fuck was he supposed to do now? Ignore the poor wee cunt? What was the point in that? He was on here to keep an eye on Mark; nothing more, nothing less. He couldn't do that without at least fucking talking to him... Simon groaned inwardly. Why the fuck did he think this was a good idea to begin with?

Aye. No bother. You look good too.<< **David**

 **Mark** >> Looks like you're close by. Local?

Somethin like that. << **David**

Sorry, am new to all this. A don't really know wit am doin.<< **David**

 **Mark** >> I get it. I've no been on here long either.

How long?<< **David**

Have ye met many people off here like?<< **David**

 **Mark** >> A few. Usually only if they can accom.

Accom?<< **David**

 **Mark** >> Accomodate. I cannae bring people home. Flate mate.

Is that all Simon was to him? A fucking flat mate?

Oh. A see.<< **David**

 **Mark** >> Disappointed? ;)

Why would a be disappointed?<< **David**

**Mark** >> You tapped me? and there's usually a reason people are on Grindr at 11:44PM.

Aye. Right enough. << **David**

 **Mark** >> So, you didn't actually answer my question.

 **Mark** >> Are you disappointed?

Simon took a shaky breath, his palms suddenly clammy as he continued to gnaw nervously as his lower lip. Mark was flirting with him. No, not with him; Mark was flirting with _David_ and it didn't feel bad... It didn't feel bad at all.

If Simon was to be completely and utterly honest with himself, he liked it. He enjoyed this playful, out-going side to his friend that he had rarely (if ever) seen. Maybe Mark had just never felt entirely comfortable around Simon or maybe Mark had spent most of his adolescence too smacked off of his wee ginger tits to worry about flirting and building strong, meaningful relationships. Aye... probably the latter.

Simon stared down at his phone, contemplating his next move. This wasn't right; he _knew_ it wasn't right. He'd heard about this, there was a whole fucking TV show based around the idea. Was he really about to Catfish his own best friend? (or fucking _flat mate_ as Mark would rather have it)...

Aye, fucking right he was.


	2. 2

**Summary for the Chapter:**

> In which Simon discovers he may be kinkier than he thought.

It was fair to say that Simon Williamson was unfamiliar with the concept of guilt. He had never been one for apologies, nor was he a blame-shifter; if there was one thing that could be said for Simon, he was always happy to hold his hands up and admit what he had done but would he apologise? Never. Guilt was not a regular feature in Simon's emotional cycle. Shit happens, you deal with it; _'The gig goes on.'_ but then so had his Grindr correspondence with Mark.

They spoke for hours, days, weeks even; both men completely and utterly enthralled with one another. Simon would skirt around the topic of “Face pics” and they would text about their day, what they were making for dinner, what their plans for the weekend were (Simon always quick with a lie... but then what was new?). Sometimes Simon wasn't sure why or how he had ever missed this side of Mark. He was sweet and clever and _funny_ , genuinely funny. Simon had never found Mark funny, not really; he was just less of an irritating cunt than the rest of their friends. Simon tolerated Mark, or at least that's what he told himself as he sprawled across their sofa, phone in hand while he scrolled through their most recent conversation.

Mark was working another late shift behind the bar at The Mousetrap and while Simon would usually take advantage of an empty flat by finding a lassie to keep himself occupied, tonight was different. Tonight he was bored, bored of everything and everyone but Mark. He missed the wee ginger fuck and he'd only been gone two hours. Two hours wasn't that long and Simon was far from needy (regardless of what his Ma would tell you) but that was still two hours of radio silence on Grindr; not a single message since Mark had told David his shift was about to start, signing off with an amorous “Don't miss me too much.”

Si was fairly certain that he had learned more about Mark Renton (the _real_ Mark Renton) in the past two and a half weeks than he ever had during their time together as friends. He had learned that Mark was a Pisces and actually believed in all that astrology bollocks, that his favourite colour was Orange but he couldn't stand the fruit. He learned that Mark suffered from anxiety, that he was medicated for it and that he never really felt comfortable enough to open up about it; not to his mates, not to his da, not to anyone. That one had hurt and Simon couldn't deny it. He knew he had no right to be offended, not when he was betraying Mark's trust the way he was but he couldn't bring himself to pull away now; not after weeks of sharing jokes, stories and intimate details about their... well, _Mark's_ life. Almost everything Simon had divulged to Mark had been completely fabricated, too scared of being caught in the lie and held accountable; finally, a transgression that Simon Williamson wasn't completely nonchalant about having committed.

Simon had given up all hope of hearing from Mark for the evening, deciding instead to stop staring at his fucking phone and go to bed where he could at least mope somewhere warm and comfortable. He laid in the dark, eyes closed while his brain worked overtime; thoughts of how Mark was getting on at work at the forefront of his mind.

Was he enjoying his shift? Was he missing their conversation as much as Simon was? Was he thinking about 'David' at all? Was he flirting with anyone? _'Is the Mousetrap even ae buftie bar?'_ Simon wondered. He had never thought to ask; never really had a reason to.

He grabbed his phone, intending to google 'The Mousetrap, Leith' when curiosity took hold and he found himself opening Grindr for what he was sure was the 100th time that evening. It was becoming habitual and Si blamed his addictive personality. A smirk tugged at the corners of Simon's mouth when the app greeted him with a new message from Mark.

**Mark** >> Hope you're no missin me too much? ;-p

What if a am? << **David**

 **Mark** >> Well then you'd be in trouble.

Trouble? << **David**

 **Mark** >> Aye.

Whys that? << **David**

 **Mark** >> Because I told you not to.

Oh aye? And what ye say goes does it? << **David**

 **Mark** >> Aye. It does.

Simon felt his stomach flip. Now _this_ was a side of Mark that he had certainly never seen. Assertive and dominant were not words that Simon would ever associate with Mark Renton but Mark, Simon was quickly learning was full of surprises.

Ye dinny seem like the authoritative type, Mark. << **David**

**Mark** >> Let me hear ye say that with my cock down yer throat.

_Fuck._ They had never done _this_ before; this was new fucking territory and Simon was just thankful that nobody was there to witness the violent shade of red that had instantly flushed his cheeks. _'Wit the fuck am a supposed tae say to that?'_ He swallowed hard and worried his lower lip between his teeth as he considered his options. He _should_ have ended it there, deleted the profile and the app and let David disappear into the night but that could have potentially hurt Mark and Simon didn't want that. He could have just brushed the comment off, made a joke of it and hope that Mark wouldn't press the issue any further.

_'Or... a could just reply? Give the needy wee cunt a bit of what he's after and then no ever think aboot it ever again. It's no like he'd even ken it's me.'_

**Mark** >> David??

Reclining back against the headboard, Simon drew a deep breath and typed out his response.

Sorry. A wis just a bit surprised. << **David**

 **Mark** >> Did I make you uncomfortable? Shite, sorry.

Naw. Nothin like that. Just... curious? << **David**

 **Mark** >> about?

The size a wit i'd be choking on ;) << **David**

 **Mark** >> Are ye askin' me for a dick pic, David?

Simon wasn't sure. Was he? Why had he said that? Of all the fucking things... he was curious about the size of Mark's cock now? ' _A mean aye, ad be lyin' if a said ad never thought aboot it; Diane seemed keen enough aw those years back. A bit a curiosity is normal like... a just wanty see wit aw the fuss is aboot.'_

Wit if a am? << **David**

 **Mark** >> Be a good boy and ask nicely.

Si could feel the undeniable pressure of a rapidly forming hard-on against his thigh as he read Mark's response; surprised at the dizzying affect the words had on his body. He cast a glance down at his tented boxers and sighed in defeat. _'Traitor.'_

Please may a see yer cock? << **David**

Better? << **David**

 **Mark** >> Much better.

 **Mark** >> I've got tae get back to my shift now but if you can wait until the morra I'll do you one better? ;)

What does that mean? << **David**

 **Mark** >> You'll see.

 **Mark** >> Talk later. X

And with that Mark was gone. The little green dot beside his name turning grey and leaving Simon both confused and painfully hard. _'Fucking tease.'_ With a frustrated groan he threw his phone back down onto the bedside table and shoved a hand inside of his boxers to wrap around his aching cock. _'It's no gay if a don't think aboot him... or what his cock would look like while am on ma knees in front of it, just waitin' fer him to give it tae me.. beggin' him fae it while he teases me; or what it would feel like, aw heavy against ma tongue while he fucks ma mouth and tells me how fuckin' braw a look suckin' him off. That a wis made to suck cock... made for him'_ Simon's breath hitched and his legs instinctively spread wider as his hand tightened around his leaking cock _,_ hand speeding up to stroke himself faster _'Made to be his good boy... Fuuuck!'_ with a stifled moan Simon came, spilling across his hand and into his own boxers.

He had laid there; sticky, wet and utterly blissed out. He would have been embarrassed at how quickly he had cum if it wasn't for the fact that he currently had bigger things to worry about... like the fact that he apparently wanted Mark Renton to skull-fuck him into oblivion all of a sudden. _'Wit the fuck am a meant tae do with that information? Is no like a can tell him.. Oh, hi Mark; how wis work? Oh, aye? Good wis it? Don't suppose you'd mind bein' a pal and lettin' me choke on yer cock?'_ Simon groaned outwardly; the short lived afterglow of his orgasm slowly subsiding and giving way to annoyance and frustration. He peeled away his soiled boxers, using them to clean himself up before tossing them to the floor where he didn't have to look at them and be reminded of what he'd just done... or of how badly he wanted to do it again.


	3. 3

**Summary for the Chapter:**

> In which Simon gets more than he bargained for.

Mark had crept in just after 3am, sweaty and exhausted from his shift. With his shoes left by the door and his keys thrown into their barely used and baron fruit bowl he made a B-line for his bedroom, letting the door click quietly behind him. Simon had laid awake listening to the other man wander around the flat as he readied himself for bed; he had counted every footstep and every creak of the floorboards while a small part of him had dared to hope for a knock at his door.

The knock never came and Simon's body eventually gave in, allowing sleep to overtake disappointment. He hadn't woken again until the early afternoon when Mark had begun hoovering outside of Simon's room. With bleary eyes and sleep-ruffled hair Simon had heaved himself up out of bed to peer accusingly out of his bedroom. “Can ye not give the house wife routine a rest fer one day? Some of us actually need sleep!”

Mark flashed him a playful grin and yelled back over the loud whirring of the vacuum. “It's after twelve, Si. Ye cannae sleep all day!”

“Last I checked you're no my Maw.” Simon grumbled, stepping fully out of his room to trudge past Mark and toward the kitchen.

“Aye but you've no issue letting me do yer washin'.”

“It should be an honour.”

“It should be _your_ job!” Mark laughed. That was the thing with Mark, Simon had thought... He was always laughing, smiling, joking like life hadn't swallowed him whole and shat him back out again on numerous occasions. This new and improved Mark Renton, shipped straight from Amsterdam was someone almost entirely new to Simon or at least he had been to begin with. Si supposed he had never realised just how funny and intelligent Mark could be; the pair of them always far too pre-occupied 'stuffing their veins with shite' as Begbie had so eloquently put it.

Real conversation had never been their strong point and Simon was almost disappointed in himself for needing the mask of an app like Grindr to truly get to know his own best friend. His thoughts drifted back to the evening before, the messages he and Mark had exchanged via the app and he couldn't help but wonder what Mark had meant when he had promised to “do him one better” than a dick pic. The uncertainty of what to expect making Simon more nervous than he had been in a very long time. You see Simon didn't _do_ nervous. Simon Williamson did cool, calm, collected and callous; a persona he had spent near 35 years perfecting, a persona he was fucking proud of. _'Ya cannae git hurt if ye don't care.'_ his Da had once told him and they were words that Simon had lived by... the words that had created 'Sick Boy'. But that wasn't who Simon was anymore, he had grown and matured or at least that's what he told himself as he pushed the fact that he was currently cat-fishing his best mate to the back of his mind.

Curiosity had got the better of him a little before 2:30pm when he had retreated to the bathroom to “shower”, swiping his phone from the coffee table as he went. He had undressed, wrapped a towel around his waist and set the shower running, finally allowing himself to check his messages as the water warmed.

**Mark** >> Good Mornin'

_Fuck._ Mark had messaged him hours ago.

Sorry for the late reply. Busy day. << **David**

Simon typed out the quick and easy lie, hitting send before he could over think anything. He hadn't had to wait more than a couple of minutes for a response. “Keen.” Simon murmured to himself with a smirk.

**Mark** >> Oh? Too busy for me? ;-)

Never! ;) **< <David**

**Mark** >> Good boy.

Simon's cock gave a dull and needy throb as he glanced over Mark's reply. This was becoming a regular occurrence; two simple words that some how shifted something inside of Simon and had him suddenly feeling all together warm, happy and compliant.

You really need tae stop that. It's no doing my cock any favours. << **David**

**Mark** >> Stop what exactly? ;-)

You know what... << **David**

Mark>> Do you no like being my good boy?

I think I like it too much! << **David**

 **Mark** >> What's so wrong with that? ;-)

_'Oh, nothin'. Only that we've been best mates since we were wains and ah suddenly can't stop thinkin' aboot how yer cock would feel absolutely decimatin' mah fuckin' wind-pipe.'_

Si groaned and brought a hand up to rub at his face in frustration. How the fuck had this happened?

**Mark** >> David?? Too much?

No. Sorry, just distracted. << **David**

 **Mark** >> Anything important?

Ah wis actually wonderin' wit ya meant last night... << **David**

 **Mark** >> Last night?

Aye. Ah asked how big yer cock is. << **David**

and ye telt me ye could 'do me one better than a dick pic...? << **David**

**Mark** >> Curiosity getting' the better of ye is it, David? ;-)

Wit if it is? << **David**

Simon would be lying if he said he didn't enjoy it; the organic back and forth, the flirtatious undertone to almost every conversation, this agonisingly slow build to something Si knew he could never really have. It was new and exciting and so fucking addictive. Picking up random lassies and paying them for their company had become commonplace for Simon before Mark's return but if he was inclined to tell the truth, it had grown stale fairly quickly; he had never been sure of why. Maybe their lack of enthusiasm? Their lack of personality? Or as Simon was slowly coming to realise... maybe it was their lack of cock?

Si was pulled from his thoughts quite abruptly when his phone began vibrating in his hand. His stomach had knotted and churned all at once when the screen flashed up at him 'Incoming video call'. ' _Fuck... fuck, fuck, fuck, fuck!'_

Mark was trying to call him... well, _David_ and not just a call but a fucking video call. In a moment of something Simon could only ever describe as panic crossed with curiosity he set himself down on the edge of the bath, pointed his camera into his towel-clad lap and answered the call.

A small part of him had expected Mark to know it was him, to recognise the generic green towel, the tiled floor of their shared bathroom, anything. He had expected to be thoroughly fucking rumbled. What Simon had not expected was Mark Renton's hard, flushed cock sitting heavy against his hip; thick, wet and clearly aching to be touched.

“...David?” Mark's voice pierced through the silence and Simon couldn't help but note how unsure and uncharacteristically vulnerable the other man sounded as he awaited a response. Simon knew he couldn't speak, not if he wanted to keep what they... _he_ had; this painfully tangled web of deceit that Simon was far too selfish to pull apart just yet.

For the first time in his life Simon kept his mouth shut and simply brought a shaky hand into view, resting it on his thigh and squeezing just slightly. He had hoped it would be signal enough that he was there. That he was watching, waiting and eager for more. He slid his hand beneath the towel by way of encouragement and Mark seemed to take the hint as he followed suit.

Simon watched ardently as Mark wrapped a hand around his cock and begun to stroke himself at a slow and languid pace. He could hear his breath hitch with every twist of his palm around the head of his prick and _fuck_ if Simon didn't want to replace Mark's hand with his mouth. He wanted to taste every inch that Mark would allow him, listen to the other man purr and keen beneath him while Simon proved just what a good boy he could be.

Si could feel his cock fattening beneath the towel that had barely been shielding his own manhood from Mark's view and without thinking on the matter too long he tugged at the knot by his waist and let it fall away. He was embarrassingly hard if truth be told, made only worse by Mark's encouraging moan of “Good boy.” as Simon's cock was finally revealed.

They took their time working themselves over. Giving in to unparalleled bliss and heady moans while trembling hands slowly subsided into bold, wanton rutting. They performed for one another completely unabashed and Simon couldn't remember the last time he had ever cum so fucking hard. Hand gripped around his leaking prick, eyes fixed on Mark and the way he fucked so desperately into his own fist as he chased release. Simon had almost bitten through his fucking lip in a desperate attempt at silencing a moan but Mark... _oh..._ Mark had cum so hard and so unapologetically loud that Simon was certain he could hear him through the wall as well as the phone.

“ _That_ wis fuckin' incredible” Mark hummed. The cunt sounded dazed and content and Simon felt a sharp spike of pride; _He_ had done that. He had made Mark feel that way. “Thank you, David.”

Pride soon shifted to guilt as Mark thanked him...or thanked David at least. He couldn't fucking take this, it was too much. With shame and remorse over-taking his post orgasmic glow Simon wiped a cum-slick hand against his thigh and exited out of the call, hoping it would appear more playful than rude.

Leaving his phone by the sink he finally stepped into the shower, dowsing himself in hot water and praying, fucking _praying_ that it would wash away the guilt and the shame he felt from betraying his best friend.

...He _had_ to make this right.

**Author's Note:**

> Thanks for reading, guys.  
> I plan on breaking this story down in to 3 chapter (possibly 4) so there is more to come with this one. It's been a while since I've written for this particular fandom so I really hope that those of you who took the time to read it enjoyed it. Comments & kudos are always appreciated and hopefully it won't take me too long to get the next chapter up.


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